Thanks for the pics A.F. Medic. Mores or less confirms my suspicions. The rifle is a professionally sporterized 98.

A backsight leaf with windage adjustment like that shown was sold 2 weeks ago on the German version of fleabay for about 50. Definitely a commercial backsight - see Olson, Chapter 7, the Mauser type "B". And if anyone out there has the book by John Speed "Mauser Original Oberndorf Sporting Rifles" they can probably find other similar-looking rifles.

Scrubbing off marks of origin and numbers that identify a weapon is, and always has been, a crime under German gun legislation. If the conversion was done in Germanyicon, and military markings were removed as part of demilitarizaion, then the rifle would have to have the gunsmith's mark and/or name applied, and a new number.

So, narrowing down my previous guestimates, that is a professionally sporterized 98, converted by a licensed gunsmith Frank Zinke of Zerbst, between the wars, and there must be a number on it somewhere. He was probably a relative of the Franz Zinke who fell in WW1, and there may well be a "Franz Zinke the 99th" who would have been interested to see one of Grandpappy's rifles.

Alas! You did not buy it, so that is the end of an intriguing and enjoyable bit of speculation.

Patrick